What kind of solitude then remains? What want? Why do we make ourselves worse than children? And what do children do when they are left alone? They take up shells and ashes, and they build something, then pull it down, and build something else, and so they never want the means of passing the time. Shall I then, if you sail away, sit down and weep, because I have been left alone and solitary? Shall I then have no shells, no ashes? But children do what they do through want of thought (or deficiency in knowledge), and we through knowledge are unhappy.

Epictetus, Discourses

What solitude is, and what kind of person a solitary man is.